CHP Loophole in SBEM

“The UK Government is serious about driving down the country’s CO2 emissions and ensuring that new developments are clearly focused on achieving a transition to a more carbon neutral built environment.
It’s an important political agenda and one that has been embraced across both the public and private sectors with some extraordinary examples of best practice.
However, the conflict between build costs and environmental specification remains and, with so many construction schemes constricted by very tight purse strings, it is no wonder that some specifiers are prepared to sacrifice long-term running cost and carbon saving benefits for the end user in order to keep the project budget on track.
There is a tight regulatory framework in place to prevent this from happening, of course, and new build projects to construct non-domestic dwellings must gain an Energy Performance Certificate (EPC) and comply with increasingly stringent Part L Regulations. The Simplified Building Energy Model (SBEM) is a calculation, delivered by a software tool, to verify that a building will achieve the Target Emission Rate (TER) required to attain an EPC and Part L compliance. SBEM is designed to assess the combination of energy producing and energy saving measures incorporated into a building design, providing an indication of the CO2 emissions.
In general terms, SBEM is a successful model that is helping to provide a framework for driving down CO2 emissions in a measurable and accountable way. However, the model is not infallible. Government enthusiasm for CHP (combined heat and power) plants as the main energy source for communal buildings means that inclusion of a CHP in any building specification is effectively a golden ticket for achieving the required TER under SBEM, which has opened up a loophole that some may exploit to reduce build costs.
It’s important to stress that the drive to encourage specification of CHPs is based on good reasoning: they enable buildings to generate their own energy, thereby taking pressure off the national grid and, in many cases, this in an excellent solution to the building’s needs. That’s not always true, however, and the fact that specification of a CHP automatically enables a project to pass the SBEM calculation, regardless of any other heating or power that is also or subsequently put into the building, means that CHPs are sometimes being specified as part of a strategy of passing SBEM rather than as a genuinely best fit solution for the building.
The problem stems from the fact that there is nothing within the SBEM calculation to ensure that specification of a CHP is the most appropriate or viable energy source for the building. As a result, some specifiers are selecting CHPs as part of a tick box approach without good engineering reasons for doing so when other options, including renewable energy sources, may offer greater environmental benefits and reduced operational costs.
More worryingly, others are using CHPs as a way to gain the SBEM calculation they need without any intention of actually running the CHP. Instead they install energy inefficient electric heating, which is cheap to purchase and expensive to run. It enables the specifier to avoid the capital costs of installing the pipework required for a more traditional system but at what cost…? A building that is not only wasteful and expensive to run, but that also puts additional pressure in the grid, rather than reducing it!
Reducing overheads and driving down carbon emissions is a high priority so we must hope that specifiers will work within the spirit of SBEM rather than exploiting its weaknesses. Fundamentally, however, those weaknesses need to be addressed if we are genuinely to improve our built environment.”